During the production of discharge lamps, a certain amount of waste products arises which contains a large variety of expensive rare-earth elements such as yttrium-oxide activated by europium (Y2O3:Eu), lanthanum-phosphat activated by cerium and terbium (LaPO4:Ce, Tb) and/or barium-magnesium-aluminate activated by europium (BaMg2Al16O27:Eu) in the form of a mixture of fluorescent substances as a coating on the inner wall of the glass body.
The general procedure applied in the hitherto customary methods of disposal and recovering is to crush the lamps by mechanical means and then separate the components of the resultant mixture of lamp fragments from one another. The U.S. Pat. No. 5,636,800 describes a process and a device for disposal and recovering of lamp glass, which suggests crushing the lamp bulbs by means of a crusher and then recovering especially the glasses of various types of lamps. This method suffers from the drawback that the fluorescent material of the crushed bulbs is mixed with powdered glass and this disclosure does not describe how the fluorescent material is separated from the powdered glass.
There have, however, also been described a method of recovering fluorescent material especially from linear fluorescent tubes in the European Patent Application EP 0 200 697 A2, wherein the bases of the fluorescent lamp are removed, and then the fluorescent material are loosen mechanically from the inner wall of the bulb by means of a stripping device, which is arranged to be inserted into the bulb from one end thereof. Then a suction device is connected to the other end of the bulb, which removes and collects the luminescent material. As a result of this, it is possible to utilize the individual components of the lamp for disposal at a higher level in that the fluorescent material of the lamp bodies can be reutilized during the manufacture of tubes. However, this process is very laborious since the fluorescent lamps must be charged to the device separately, which will be particularly difficult in the case where not only straight fluorescent tubes but also circular or otherwise curved e.g. compact fluorescent lamp tubes are to be reprocessed.
At the different stages of the process of manufacturing discharge lamps, different kinds of faulty glass bodies emerge. Up to the exhausting stage of the production of fluorescent lamps, the tubes do not contain mercury. Up to this point, it is possible to reprocess the faulty lamp glass bodies rolling out from the production line regardless the need of treating the mercury waste.
Faulty glass bodies emerging at different stages of the lamp manufacturing process require different treatment of recovering. Just after coating the inner wall of the glass bodies with fluorescent material, the coating suspension contains binding material too, which has to be removed from the suspension during recovery. At another stage of the lamp making process, the coating is burned out properly, so it does not contain binding material any more. Finally, just before the exhausting of the glass bodies, they are sealed and provided with lead-in wires and tungsten coils coated with emission material.
Thus, there is a particular need to provide an easy and economic process, by which a high-level recovery of the fluorescent material of the faulty lamps is possible taking into consideration the different kind of faulty glass bodies emerging at different stages of the lamp making process.